93 4.0 rough Idle and popping

B

Boy And A Bag

New Member
Joined
Oct 28, 2025
Messages
6
Location
Plano TX
Good evening gents,

I have a customer car here that had a no start concern and unfortunately he threw the parts cannon at it before it came to me. He also threw away all of the original parts…

He did the crank sensor, distributor and fuel pump and it still wouldn’t work for him.

I got it to start now with a crown crank sensor but it idles very rough and pops constantly from the exhaust. When starting, it will also shoot flames from the intake if I open the throttle plate enough. I only had to do this originally before the crank sensor install to get it to start.

It will run smooth once I rev it to 2000+. I’ve checked fuel pressure and we have 40 at the rail and I’ve cleaned and tested the fuel pump and filter to be sure. I’ve also made sure it was in time and checked the wires, distributor and coil. It’s running lean as the plugs are ghost white. We have good compression, 150+ per cylinder

I am not too familiar with these jeeps as I usually work on 98+ cars for my business. This is my first time ever on a forum so I apologize if I am covering something that’s been discussed.

Thank yall in advance!
 
does check engine come on, if yes then you will have codes. the right plug is champion RC12lyc
 
I had to laugh at this one. Years ago I worked at a bosch importer. The CEO, an arrogant German dude had just bought a new Cherokee and was headed for a ski trip that weekend. He asked my to install a set of the then new Bosch Plat plugs. I did just that. I also put them in my 350/suburban that weekend. He returned and said this thing runs like shit, put the old plugs back in, Champions BTW. That fixed his jeep and I also removed the ones from my sub after a couple days of driving it. It ran like shit, the idle was noticeably lower, MPG's dropped to 6mpg and it generally ran like it was dragging a car behind it. Put the AC's back in, and back to normal. I'm not much on "voodoo" of use this brand or else, and I dont really like Champ plugs, but sometimes its best to stay away from all the BS snake products. Not saying plugs are the things only problem but I personally would put champs back in it.
 
Well folks I feel like an idiot..

When I was reverting everything back to stock I had put the original distributor back on and put the wire back in sequence how he had it..

Well, I had my buddy come out and lay a fresh set of eyes on it and the golden rule of car repair bit me in the ass. “It’s always the simplest thing” , well he comes out and tells me that the firing order is completely flipped meaning that it was in order going the wrong way. Idk how this thing was running nor do I know how the hell I managed to miss that.

Anyways, I felt like I should give yall and update! We’re going to make sure we get everything to OEM plus spec now that this will be my customers new daily!

He also wants to add A/C but it had a compressor on a crude bracket and the switches but nothing else. I think it will be a nightmare to figure out what he does and doesn’t have so we may just go with an aftermarket kit, any specific recommendations?
 
glad you got it going and thanks for keeping us posted. I made the same mistake in my early yrs.
 
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